Screen structure for hammer mills



Feb. 27, 1951 c. A. RIETZ 2,543,599

SCREEN' smuc'ruaz FOR HAMMER mus Filed April 6, 1946 3 Sheets-Sheet 1FII'5 L INVENTOR. Car/ 14. R 119/;

ATTORNE V Feb. 27, 1951 c. A. RIETZ 2,543,599

SCREEN STRUCTURE FOR HAMMER MILLS Filed April 6, 1946 3 Shuts-Sheet 2FIE-'I E A TTORNEY W o 5 2 a w M m a n 3 a "w 3 o 5 f M a 8 I 6 8 bzrmzJERLM/ 22 32 2 J 7 54 1 W 5% 1 L a M F F C 7 3 a wv w a 5M 3 7 B I my, 4,./(M\\\\ l 23, a I 7 3 A 3 x 9 2% mm 3 w.

Feb; 27, 1951 c. A. RIETZ scam-m STRUCTUREFOR HAMMER ums 3 Sheets-Sheet3 Filed April 6, 1946 ATTORNEY INVENTOR.

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Patented Feb. 27, 1951 SCREEN STRUCTURE FOR HAMMER MILLS cm A. mm, SanFrancisco, Calif., assignor to I Rictz Manufacturing Co., San Francisco,Calif., a corporation of California Application April 6, 1946, SerialNo. 660,256

2 Claims. (Cl. 241-88) This invention relates generally to machines forthe disintegration of various materials. More specifically it relates tomachines of the type wherein hammers carried by a rotor act upon thematerial to effect disintegration.

An object of the invention is to generally improve the disintegratingefliciency of machines of the above type particularly with respect tothe disintegrating action secured by impact of the particles. A featureof the machine which assists in the attainment of this object is theprovision of anvil-like impact surfaces of substantial length in thedirection of the axis of the machine rotor, and which are faced in adirection opposite to the direction of rotation of the rotor. As will bepresently explained the provision branch means makes possible areverberatory impact action.

A further object of the invention is to gen-' erally improve upon hammerdisintegrators of the vertical type such as disclosed in my Patent No.2,153,590.

Additional objects of the invention will appear from the followingdescription in which the preferred embodiments have been illustrated indetail in conjunction with the accompanying drawing.

Referring to thedrawing- Figure 1 is a side ,elevational view in sectionillustrating a disintegrating machine incorporating the presentinvention.

Figure 2 is a section taken along the line 2-2 of Figure l. v

Figure 3 is a sectional detail on an enlarged scale taken along the line33 of Figure 1.

Figure 4 is a detail illustrating the construction of the top flange ofthe rotor, with this flange having a provision to prevent undue wearupon the heads of the hammer retaining rods.

Figure 5 is a cross-sectional detail taken along the line 5-5 of Figure3. p

Figure 6 is a section taken along the line 6-4 of Figure 1.

Figure 7 is an enlarged detail in section illustrating a modified formof screen assembly.

Figure 8 is a side view of the screen assembly as shown in Figure 7,with parts bein broken away.

Figure 9 is a sectional detail like Figure 7 but illustrating anotherembodiment of the screen assembly.

Figure 10 is a side view of the embodiment shown in Figure 9, with partsbeing broken away. The machine illustrated in the drawing is a 2 Rietz2,153,590. Such a machine utilizes a disintegrating rotor mounted upon avertical axis and provided with a plurality of spaced hammers to afforda zone of operation of substantial vertical extent. A cylindrical shapedscreen substantially entirely embraces the zone of operation and iscarried by the main housing or frame of the machine. The housing isformed 7 to provide an inlet opening at the upper end of the screenwhereby material supplied through this opening is fed to the'zone ofoperation. The housing also provides an annular outlet opening at thelower end of the screen for de livering material which is passed by thescreen as a result of the disintegrating action of the hammers.Disintegrating machines of this type afford a relatively high capacityand have been found well suited to the disintegration of a wide varietyof materials.

Referring to Figures 1 to 5 inclusive of the tical shaft [3. The upperend of this shaft is supported from a suitable thrust hearing it and iscoupled to a suitable electric motor IE, or provided with other suitablemeans for driving the same. The opening or passage ll of the housingserves to supply material to be disintegrated to the zone of operationof the rotor. The shaft can be provided with breaker blades ii togenerally break up coarse material before feeding the same to the rotor.

The rotor is surrounded by the substantially cylindrical shaped screenassembly I8, and as will be presently explained material acted upon bythe disintegrating hammers is forced through this screen assembly forultimate discharge. A skirting IQ of a type to be presently explainedgenerally surrounds the screen assembly l8, and the space 2| immediatelysurrounding the screen communicates with the annular discharge opening22 formed in the housing base 23. In actual installations the machine ismounted in such a fashion that the material discharging downwardlythrough opening 22 is received by a suitable hopper or conveying/"beanswhich underlies the machine.

The rotor assembly l2 consists of a lower annular flange 26 (Figure 1)which is accommodated on shaft l3, together with a plurality ofoverlying stacked flanges 21 and a top flange 28. The disintegratinghammers 29 are each provertical type hammer mill of the type shown invided with inner arcuate portions 3| (Figure 2) amasea hammersdesignated 38, are preferably'iof special I construction for the purposeof aiding in downward movement of material being disintegrated. Thusthese hammers have head portions 36a and shank portions 36b whichconnect the head portions with the arcuate anchoringjportions 3|.Portions 36b are disposed at an inclination to the horizontal as shownin Figure 5, assuming rotation from right to left as indicated in thisfigure. They act in effect as propelling means tending to urge thematerial downwardly into and through the zone of disintegration. Inaddition portions 361) tend to cut up material being fed downwardly, andin general they tend to prevent bulky material from riding upon the topof the rotor assembly, rather than feeding downwardly as desired.

To prevent undue wear upon the nuts or heads 34, of the anchoring rodsand upper face of the top flange 28 is provided with ribs 31. Theseribsare located in advance of the heads 34, and they haveinclined faces38 tending to deflect the material to prevent direct impact contact withthe heads 84.

The lower end of the rotor shaft is shown journaled as by means of ballbearing assembly 4! to the annular casting 42. This casting is securedto the base of the housing by screws 43, and it affords an annularpassage 4d underlying the zone of operation of the rotor. It has beenfound desirable to form passage 44 with divergent inner and outer wallsas illustrated (Figure 1), because such construction has been found toprevent clogging when the machine is operated to provide a secondarydischarge in the manner disclosed in my Patent 2,325,426. When such asecondary discharge is not desired the passage 44. is suitably blockedoff by application of a closure plate or screen.

Previous reference has been made to the skirting means i9 surroundingthe exterior oi. the screen assembly it. As shown in Figure 2 the baseof the machine connects integrally with the upper part of the housing bythe vertical struts 46, 41. The outer faces of these struts conform to acylindrical surface, and are engaged by the sheet metal sections 48, 49and 50. Sections 48 and 45 can be integrally attached as illustrated,and their vertical edges 52 are brought together in overlapping relationto the vertical edges 53, 54 of the section 50. .Suitable means such asthe hinged bolts 55 are employed for releasably retaining the sectionstogether.

The wall portions 56, 51, 58 of sections 48, 49, 50 are inclinedoutwardly (Figures 1, 2) where by material which contacts their innerfaces may be more readily dislodged, as will be presently explained.Such outward inclination may be utilized to provide openings tofacilitate introduction of a tool or rake to dislodge accumulatedmaterial, or if desired such openings may be closed by suitable means.

The screen assembly illustrated particularly in Figure 3 consists of twosemi-cylindrical screen sections iii, the adjacent vertical edges ofwhich are attached to the angle irons 82. Normally these angle irons areheld together by a plurality of c clamps 63, 64, and one or more of theclamps 64 can be provided with extension 4 88 to abut the vertical stud41 in order to prevent rotation of the screen. The screen in thisinstance is formed of sheet metal with opening 6'! of suitable diameterto pass the size of disintegrated material desired.

Upon the inner face of the screen but disposed in such a manner as tonot interfere with rotation of the hammers, I provide {means tending toform a plurality of anvil-like impact faces. In this particularembodiment such anvil-like faces are formed by a plurality of verticallyextending strips 68 which are distributed circumferentially about therotor and attached to the screen 6!. Assuming rotation in acounterclockwise direction as viewed in Figure 3, the faces 68a ofstrips 68 are faced opposite to the direction of rotation, and afford areverberatory action in connection with the impacting and disintegrationof material, in a manner which will be presently explained in greaterdetail.

In the distintegration of certain types of iibrous material, as forexample wood pulp fibre being processed, an objectionable dehydration ofthe cell structure occurs to the detriment of the finished product. Ithas been found possible to prevent such dehydration by forciblyinjecting water into the zone of operation of the machine. Thus aplurality of nozzles H are provided above the rotor and dischargedownwardly through the opening l1. These nozzles are connected to asuitable source of water or water solution under pressure. In addition aplurality of nozzles 12 are provided about the screen assembly, andthese nozzes are arranged to forcibly discharge coarse spays of wateragainst the sides of the screen. The water is applied to the screen withsuch force that a considerable amount of the water passes through theopenings of the screen into the zone of operation. In this manner wateris injected into substantially all parts of the zone of operation of therotor, and therefore fine droplets or a mist of added water is providedin such a manner as to prevent dehydration of the cell structure of thefibre.

In the treatment of certain types of material such as peanut meal, ithas been found that there is a tendency for this material to accumulateand clog the outlet opening 22. To effect dislodgment of any suchaccumulations without interfering with continued operation of themachine, I provide a plurality of agitating rods or rakes 13. These rodsextend loosely through the openings l4, and their upper ends areprovided with suitable handles 16. The rods are a suitable length toextend downwardly through the annular openin 22. To dislodge anyaccumulation of material in opening 22, the operator grasps handle I6and then by imparting movement to the rod the undesired accumulations ofmaterial are agitated and caused to be ejected.

Operation of the machine described above can be reviewed as follows: Themachine is placed in operation with the rotor turning at a suitablespeed, such as speeds of the order of 2700 R. P. M. or more. Thematerial to be distintegrated is supplied through the hopper II andpasses into the zone of operation through opening ll. As the materialenters the zone of operation of the rotor it is engaged by the uppermost hammers 36 and by virtue of the inclined hammer portions 36b, thereis a. downward feeding action. Within the zone of operation the materialis repeatedly impacted by the forward faces of the hammers, andparticles propelled from the hammers by virtue of such impacts strikeand rebound from the inner face of the screen, and particularly theystrike and rebound from the anvil-like faces 56a. of the strips 68.Material rebounding from the faces 68a is again struck by the hammers,and therefore there is in effect a continual impacting of the materialback and forth between the hammers and the faces 60a, to afford what canbe termed a reverberatory impact action. By virtue of such action highlyefficient disintegration is provided, thus making possible high capacitywithout wasteful utilization of power to produce the desired degree ofdistintegration. when the material has been reduced by impacts to poperfineness it is passed by the apertures in screen GI, and then fallsdownwardly through the annular discharge opening 22. When fibrousmaterial is being handled and where it is desired to prevent dehydrationof the cellular structure, water is supplied to the nozzles ll, 12whereby added droplets of water are forcibly introduced into the zone ofoperation to intimately associate such water with the material beingdistintegrated. In this manner it has been found possible to preventcellular dehydration, thus affording a relatively high qualitydistintegrated product suitable for further processing. As an example offibrous material which can be treated in this manner reference can bemade to various types of wood fibre which can be distintegrated toproduce various types of paper stock, without the objectionabledehydration of the cellular structure experienced with ordinary hammertypes of mills.

In handling materials which are relatively adherent and tend toconglomerate together when disintegrated, like peanut meals, theinclined curtain walls 56, 51, 58 tend to be self defecating andfacilitate gravity and manual dislodgement of any accumulated material.

Should any part of the opening 22 tend to become clogged byaccumulations of disintegrated material, the opening can be readilycleared by manual use of the rake 13.

The reverberatory effect previously described can be produced by meansother than that incorporated in the foregoing embodiment. Thus as shownin Figures 7 and 8, the screen assembly 8| consists of a relativelyfragile sizing screen 82, an exterior relatively strong backing screen83 having relatively coarse openings, and an inner covering plate 84provided in this instance with staggered slots 86. These slots aredisposed to register with certain of the openings in the backing screen83. The vertically extending faces 81 afforded by the slots 86 formanvil-like surfaces for impacting the material being disintegrated insubstantially the same manner as the forward faces of the strips 68 ofthe first described embodiment.

In the embodiment of Figures 9 and 10 the assembly 88 consists of arelatively fine and fragile sizing screen 89, an outer backing screen 9|having relatively coarse perforations, and an inner plate-like member 92provided with square openings 93. These openings provide verticallyextending anvil-like surfaces 94 for impacting the material beingdisintegrated.

Subject matter disclosed but not claimed herein is disclosed and claimedin my co-pending application Serial No. 166,277, filed June 5, 1950.

I claim:

1. In a disintegrator, a rotor mounted upon a vertical axis and providedwith a plurality of circumferentially and vertically spaced hammers tothereby form a zone of operation of substantial vertical extent, agenerally cylindrical shaped sizing screen substantially entirelyembracing the zone of operation, a housing serving to support the rotorand the screen, the housing providing an inlet opening at the upper endof the screen for feeding material to be disintegrated to the zone ofoperation, and a rigid plate-like member extending over the inner faceof the screen, said member being provided with a plurality of openingsdistributed over the entire area of the screen, each of said openingsbeing dimensioned whereby said plate-like member provides upstandinganvil-like impact surfaces extending generally parallel to the axis ofthe rotor for a substantial vertical distance and faced in a directionagainst the direction of rotation of the rotor, said openings beingstaggered in a vertical direction whereby the vertical length of eachimpact surface overlaps the vertical length of an adjacent surface.

2. In a disintegrator, a rotor mounted upon a vertical axisand providedwith a plurality of circumferentially and radially spaced hammers tothereby form a zone of operation of substantial vertical extent, agenerally cylindrical shaped screen substantially entirely embracing thezone of operation, a housing serving to support the rotor and thescreen, the housing providing an inlet opening at the upper end of thescreen for feeding material to be disintegrated to the zone ofoperation, and a rigid plate-like member extending over the inner faceof the screen, said member being provided with a plurality of openingsdistributed over the entire area of the screen, each of said openingsbeing dimensioned whereby said plate-like member provides upstandinganvil-like impact surfaces extending generally parallel to the axis ofthe rotor and of substantial vertical extent and faced in a directionagainst the direction of rotation of the rotor, adjacentcircumferentially spaced openings being at different elevations wherebythe vertical extent of each opening overlaps the vertical extent of anadjacent opening.

CARL A. RIETZ.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date Re. 5,936 Moore June 30, 1874 Re.8,258 Meech May 28, 1878 40,217 Sellers Oct. 6, 1863 249,793 Paden Nov.22, 1881 257,841 Bellinger May 16, 1882 265,957 Gates 1 Oct. 17, 1882297,755 Case Apr. 29, 1884 306,275 Moller Oct. 7, 1884 399,518 Good"9..---- Mar. 12, 1889 440,537 Boyd Nov. 11, 1890 665,935 Rudolph Jan.15, 1901 1,018,440 Paul Feb. 27, 1912 1,422,761 Hartman July 11, 19221,574,436 Martin Feb. 23, 1926 1,767,921 Gately June 24, 1930 1,977,771McMahan Oct. 23, 1934 2,153,590 'Rietz Apr. 11, 1939 4 2,199,729Peterson May 7, 1940 2,241,848 Eckart May 13, 1941 2,273,405 Hoehn Feb.17, 1942 FOREIGN PATENTS Number Country Date 539,524 Great Britain Sept.15, 1941

